Thanks for the heads up MLParkinson
And well done with the fantastic work you're doing - with a system less than 500mm FL! I would be happy to stick with the shorter focal length systems - deep sky galaxies haven't captured my attention yet. Wide field nebulae are what I am finding most interesting atm, so a system with a FL less than 1000mm is what I'd be looking at. Hey, would a 8" f4.0 newt imaging circle cover a full frame DSLR sensor? Haven't found much info about that.